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Chem Final I

STUDY
PLAY
How many grams are there in 3.58 short tons? Show all work, all units, 1lb= 16 oz, 1 short ton= 2000lb.
3.58 short ton= 2000 lb/ 1 short ton X 16 oz./ 1lb X 1 g/ 0.03527 oz = 3.25E 6 grams
Chap. 1
Sample A- Mass of Sample:1.518g MofFE:1.094g MofO: 0.424g
Sample B- 2.056, 1.449g, 0.607g
Sample c- 1.873g, 1.335g, 0.538g
Sample A- 1.094/ 0.424= 2.58
Sample B- 1.449/ 0.607= 2.38
Sample C- 1.335/ 0.538= 2.48
No because the ratios of M(iron) to M(oxygen) are all different.
Chap. 1
The density of osmium metal ( a platinum- group metal) is 22.5 g/cm^3. Express the density in SI units (kg/m^3).
22.5g/cm^3 = 10^-3 kg/1g x 10^6 cm^3/ 1m^3= 2.25x10^4 kg/m^3
Chap. 1
Calculate the relative abundance of each isotope of Boron from the following data:
Isotope Mass: Isotope Mass (amu): Average Atomic
B-10: 10.013=
------------------------------ 10.812
B-11: 11.009=
B-10= x
B-11= y
*x+y= 1--> x= 1-y
** x(10.013)+y(11.009)= 10.812
----> (1-y)(10.013)+ 11.009y= 10.812
-----> 10.013- 10.013y+11.009y = 10.812
-10.013 -10.013
----> .996y=.799
***-----> y=.8022088353X100= 80.221% (B-11)
**** B-10= 100%- 80.221%= 19.780%
Chap. 1
An element has three naturally occurring isotopes with the following masses and abundances:
Isotopic Mass (amu)----- Fractional Abundance
I- 38.964------ 0.9326
II- 39.964------ 1.000X 10^-4
III- 40.962------ 0.0673
(Isotope Mass)(Fractional Abundance)=
I- 38.964(0.9326) = 36.3378264
II- 39.964(1.000X 10^-4)= .0039964
III- 40.962(0.0673)= 2.7567426
----> I + II + III= 39.0985654
**------> 39.10 Potassium

Chap. 1
A 1.50 g sample of nitrous oxide (an anesthetic, sometimes called laughing gas) contains 2.05 X 10^22 N2O molecules. How many nitrogen atoms are in this sample? How many nitrogen atoms are in 1.00 g of nitrous oxide?
NO= 1.50g
N2O= 2.05 x 10^22
*---> 1.50g NO/ 2.05X10^22= 1g/ x
------> 1.3666667 X 10^22 nitrogen atoms--> 1.37 X 10^22
= ------> 2(1.37x10^22) = 2.74x 10^22 nitrogen atoms in 1 g of N2O
** Nitrogen=
----> 2.05x10^22 N2O= 2N atoms/1 N2O= 4.10x10^22 nitrogen atoms
Chap. 1
How many significant figures are there in the value 4,750,330?
a. 7
b. 6
c. 5
d. 4
e. 3
b. 6
Chap. 1
Which of the following sets of numbers have the same number of sig figs?
1. 3.55E-3 2. 3.55E3 3. 3,550,000
a. 1 and 2
b. 1 and 3
c. 2 and 3
d, 1,2,3
e. none of them
d. 1,2,3
Chap. 1
The number of significant figures that should be reported for the answer the mathematical computation 142.000- 41.9903 is
a. 2
b. 3
c. 4
d. 5
e. 6
d. 5
Chap. 1
Liquid propane boils at -42C. What is its boiling point on the Kelvin scale?
a. 231k
b. 256k
c. 273k
d. 315k
e. 345k
a. 231k
Chap. 1
The average velocity of oxygen molecule at 1000 is 8X 10^4 cm/s. Which of the following calculations would convert this value to the velocity in miles per hour?
e. 8X10^4 cm/s X 1 in/ 2.54 cm X 1 ft/ 12 in X 1 mi/ 5280 ft X 3600s/ 1 hr

Chap. 1
A piece of indium weighing 15.442g is placed in 49.7 cm^3 of ethyl alcohol (d= 0.789 g/ cm^3) in a graduated cylinder. The alcohol level increases to 51.8 cm^3. The best value for density of indium from these data:
a. 7.353 g/ cm^3
b. 7.35 g/cm^3
c. 7.4 g/ cm^3
d. 9.21 g/ cm^3
e. 9.2 g/ cm^3
c. 7.4 g/cm^3

Chap. 1
How many protons, neutrons, and electrons are in the tin(II) ion 119, 50 Sn^ 2+? (p,n,e)
a. 119, 50, 119
b. 50, 69, 50
c. 50, 69, 48
d. 69, 50, 69
e. 50, 119, 52
c. 50p, 69n, 48e
Chap. 1
A certain element is listed as having 63.5 atomic mass units. It is probably true that it:
a. a mixture of isomers
b. a mixture of allotropes
c. a mixture of neutrons
d. a mixture of ions
e. a mixture of isotopes
e. a mixture of isotopes
Chap. 1
The mass spectrum of an element with two naturally occurring isotopes is shown below. Its atomic mass would be best estimated as (chart).
c. 63.6

Chap. 1
Choose the pair of names and formulas that DO NOT match:
a. Sodium Sulfite Na2S
b. Calcium fluoride CaF2
c. Potassium permanganate KMnO4
d. Aluminum bromide AlBr3
e. Iron (III) oxide Fe2O3
a. Sodium Sulfite--- Na2S

Chap. 1
The formula neodymium sulfate is Nd2(SO4). On the basis of this information, the formula for the nitride of neodymium would be expected to be:
a. Nd2(NO2)3
b. Nd2N2
c. Nd(NO3)3
d. Nd(NO2)3
e. NdN
e. NdN

Chap. 1
Treatment of sodium borohydrate with sulfuric acid is a convenient method for the preparation of diborane:
__ NaBH4+ ___H2SO4---. ___ B2H6+ H2+ Na2SO4
a. 1
b. 2
c. 3
d. 4
e. 5
b.2
Which of the following equations is (are) balanced?
1. NaCl + Pb(NO3)2---> PbCl2 + NaNO3
2. (NH4)2Cr2O7 ---> N2 + 4H2O + Cr2O3
3. FeO4 +3CO ---> 3Fe + 3 Co2
a. 1
b. 2
c. 3
d. 1 and 2
e. 1,2, 3
b. 2
What is the ratio of oxygen atoms to hydrogen atoms in the mineral carnotite K2(UO2)3 (VO4)2 X 3H2O:
a. 8:3
b. 8:6
c. 9:6
d. 17:3
e. 17:6
e. 17:6
END CHAP.1
Calculate the percentage composition for each of the following componds (to three sig digs):
(a) CO2
*C+O2= 12.01 + 2(15.99) = 44.008
** C- 12.01/ 44.008= .273 X 100= 27.3%
*** O2 - 2(15.99)/ 44.008 = .727 X 100= 72.7%
Malonic acid is used in the manufacture of barbiturates (sleeping pills). The composition of the acis is 34.6% C, 3.9% H, and 61.5% O. What is Malonic acid's empirical formula?
*C- 34.6g x 1mol/ 12.01g C = 2.88
H- 3.9g H X 1mol/ 1.01g H= 3.86
O- 61.5 O x 1 mol/ 15.999g O = 3.84
** C- 2.88/ 2.88= 1 X 3 = 3
H- 3.68/2.88= 1.34 X 3= 4.02--> 4
O- 3.84/ 2.88= 1.33 X 3 = 4
** C3H4O4 ****
Nickel (II) cholride reacts with sodium phosphate to precipitate nickel (II) phosphate and another.
(a) Write a balanced equation for this reaction.
(b) What is the amount (in grams) of nickel (II) phosphate produced from 42.6g of sodium phosphate?
(a) 3NiCl2 + 2Na3PO4 ---> Ni3(PO4)2 + 6NaCl
(b) 42.6g Na3PO4 x 1mol/ 163.9392 Na3PO4 X 1mol/ Ni3(PO4)2/ 2 mol Na3PO4 X 366g Na3PO4/ 1mol Na3(PO4)2
= 43.5 g Ni3(PO4)2
Nitric acid HNO3 is manufatured by the Ostwald process in which nitrogen dioxide, NO2, reacts with water.
3NO2 (g) + H2O ---> 2HNO3 + NO
Suppose a vessel contains 4.05 grams NO2 and 6.72 g H20.
(a) What is the limiting reactant?

(b) How many grams of HNO3 could be obtained?
(a) NO2
(b)
NO2-- 4.05g NO2 X 1 mol/ 46.0047g NO2 x 2 mol HNO3/ 3 mol NO2= .05868 = .059

H2O-- 6.72g H2O X 1 mol H2O/ 18.01g H2O X 2 mol HNO3/ 1 mol HNO3 = .07458= .075

Limiting reactant: .059 mol HNO3 X 63.0137 g HNO3/ 1 mol HNO3= 3.7178= 3.72g HNO3
Write the oxidation- reduction half reactions for the following reactions and balance the overall reaction.
(a) Mn^2+ + BiO3^- ----> MnO4^- +Bi^3+

(b) Cr2O7^-2 + I^- ---> Cr^3+ + IO3^-
(a) [ Mn^ 2+ ===> Mn^7+ + 5e- ]= 2Mn ---> 2MnO4 + 10 e-
---> 5[ 2e- +BiO3^- ===> Bi^3+] = 70 e- + 5BiO3---> 5Bi
*---> 2Mn + 5BiO3 ---> 5Bi + 2MnO4

(b) [ 6e- + Cr2O7 ---> 2Cr^3+] ===> 6e-+ Cr2)7----> Cr^3+
-----> [I^- (+6) ---> IO3^-] 9 ===> 9I---> 9IO3 + 9e-
**----> 9I +Cr2O7---> Cr+ 9IO3
What is the percentage of chlorine in DDT, C14H9Cl5?
d. 50.0
A given hydrocarbon is converted completely to water and carbon dioxide, and the mole ratio of H2O to CO2 is 1.33:1.00. The Hydrocarbon could be?
e. C3H8
Which of the following contains the greatest mass of chromium?
b. 25.0g CrO2
Ammonia can be made by reaction of water with calcium cyanamide:
CaCN2 + 3H2O ---> CaCO3 + 2NH3

When the equation is properly balanced, the sum of the coefficients is:
d.7
All of the following are weak acids except:
e. HNO3
All of the following are strong acids in aqueous solution except:
a. HClO2
All the following are strong electrolytes except:
b. H3PO4
The oxidation number of chromium in sodium chromite, NaCrO2, is
e. +3
Which of the following reactions is an oxidation-reduction reaction?
b. NH4NO3 ---> N2O + 2H2O
The formation of an anion from an atom would be called:
e. reduction
END of 3&4
SnO2 + 2CO --> Sn + 2CO2 DeltaH= +14.7Kj
a. Calculate the amount of heat absorbed when 5.60g of tin are formed.
b. Calculate the volume of CO2 evolved (measured at 745mmHg and 23C) when 5.60 g of tin are formed.
a. 5.60g Sn x 1mol Sn/ 118.71g Sn x 2mol CO2/ 1 mol Sn= .094 mol

PV= nRT ---> V= nRT/P
===> .094 mol (0.0821)(296k)/ (745/760) = 2.2843504/ .98026= 2.33 g/L